The invention relates to the preparation of mesoporous organic-inorganic hybrid materials which may be used in the purification of gases.
Current separation techniques (cryogenic distillation or adsorption on zeolites) and techniques for the purification of industrial gases (cryogenic distillation or catalysis) are not always optimized, either in economic terms (cryogenics in the case of small quantities) or in terms of gas purity (the oxygen obtained by adsorption contains 5% of argon, for example). Many studies have shown that gases such as oxygen, hydrogen or carbon monoxide react selectively and reversibly with transition metal complexes. Thus, cobalt(II) complexes of cyclam or of cyclene are known to coordinate dioxygen strongly in solution (R. Machida, E. Kimura, M. Kodama, Inorg. Chem., 1983, 22, 2055).
However, the lifetime of oxygen-containing complexes in solution is limited as they can undergo irreversible degradation reactions ((A. E. Martell, A. K. Basak, C. J. Raleigh, Pure Appl. Chem., 1988, 60, 1325-1329). Furthermore, these species cannot be deoxygenated simply by decreasing the dioxygen partial pressure. Immobilising the ligand on a solid matrix should facilitate use and limit degradation of the oxygenated species and improve the reversibility of the reaction.
Direct synthesis in a micellar medium of mesostructured silicas having large specific surface areas (800-1400 m2.g−1) with a very narrow pore distribution which is adjustable between 2 and 10 nm was discovered in 1992 (J. S. Beck, J. C. Vartuli, W. J. Roth, M. E. Leonowicz, C. T. Kresge, K. D. Schmitt, C. T. Chu, D. H. Olson, E. W. Sheppard, S. B. Higgins, J. L. Schlenker; J. Am. Chem. Soc. 1992, 114, 10834). This new family of mesoporous materials (MTS: abbreviation of the English term “micelle-templated silica”), is obtained from the cooperative assembly of an inorganic phase round an organic phase consisting of surfactants in a micellar concentration (J. Y. Ying, C. P. Mehnert, M. S. Wong; Angew. Chem. Int. Ed., 1999, 38, 56-77). Once the material has been formed, elimination of the surfactant liberates the porosity of the inorganic framework and thus leads to a porous organised inorganic phase.